This invention relates generally to the field of electronic devices, and more particularly to a fuse with a low fusing current and methods for making and using the same.
Modern electronic equipment such as televisions, telephones, radios, computers and personal communication systems are generally constructed of solid state devices. Solid state devices are preferred in electronic equipment because they are extremely small and relatively inexpensive. In addition, solid state devices are very reliable because they have no moving parts, but are based on the movement of charge carriers.
Solid state devices may be transistors, capacitors, resistors, fuses and other semi-conductor devices. Typically, such devices are fabricated on a substrate and interconnected to form an integrated circuit. Integrated circuits use fuses for die identification, analog trim functions and to selectively bypass non-functional circuitry such as in a faulty dynamic random access memory (DRAM).
One type of fuse used in integrated circuits is the polysilicon fuse. Polysilicon fuses are cost efficient and reliable but require a large potential of about five volts to be successfully blown. The large potential is problematic for low voltage processes and equipment and/or equipment that use electrical means to blow fuses through a serial interface.
To accommodate lower voltage and other requirements, polysilicon fuses have been silicided. The thin silicide layer provides a low resistance path across the fuse that allows the fuse to be blown by a potential of about three volts. Silicided fuses, however, require that a high amount of power be rapidly introduced into the fuse to blow both the silicide layer and the polysilicon layer at the same time. The high amount of power requires large fusing resistors which take up valuable area on an integrated circuit chip and can cause damage to the chip during fusing.
The present invention provides a fuse and a method that substantially reduce or eliminate problems and disadvantages associated with previous systems and methods. In particular, the fuse comprises minimal or no resistive polysilicon in the fusing element to reduce the necessary fusing current and to allow use of polysilicon fuses in low voltage integrated circuits.
In accordance with one embodiment of the present invention, a fuse for an integrated or other suitable circuit includes a first contact element and a second contact element. A fusing element is coupled between the first and second contact elements. At least a majority of the fusing element comprises silicided material.
More specifically, in accordance with a particular embodiment of the present invention, a polysilicon layer extends across at least part of the first and second contact elements. In this embodiment, the polysilicon layer may taper down to a minimal thickness for the fusing element or taper off in the contact elements in which case the fusing element is comprised solely of a silicide layer. The first and second contact elements may each include a transition area in which the width of the fuse thins after tapering of the polysilicon layer to provide a reliable and well-defined fusing element.
Technical advantages of the present invention include providing an improved fuse and method for an integrated or other suitable circuit. In a particular embodiment, the fuse fuses at a low voltage and/or power to extend down the range of voltages in which polysilicon fuses can be used. In addition, standard components may be used for the fusing detector and smaller fusing transistors used in connection with the fuse. Thus, the size of the fuse cell is reduced.
Another technical advantage of one or more embodiments of the present invention includes providing a fuse having a substantially silicided fusing area. In particular, resistive polysilicon is minimized or eliminated from the fusing area to lower the fusing current and reduce damage to the integrated circuit during fusing. In addition, the possibility of partial fusing is reduced.
Other technical advantages of the present invention will be readily apparent to one skilled in the art from the following figures, description, and claims.